BEIRUT (AP) -- The death toll from infighting between rival Islamic rebel groups in an eastern Syrian town has risen 68 killed, with some shot after being captured alive, activists said Friday.
The Britain-based Syrian Observatory for Human Rights said battles raged Friday for a second day in the oil-rich Deir el-Zour province near the Iraqi border. It said the fighting concentrated in the village of Haseen after members of the al-Qaida breakaway group known as the Islamic State of Iraq and the Levant were forced out of the nearby town of Bukamal.
Rebels from the Islamic State and fighters of the al-Qaida-linked Nusra Front and other Islamic groups have been fighting each other in the province for weeks over territory previously captured from President Bashar Assad's forces, including oil fields.
The Observatory said 68 fighters died in fighting around Bukamal on Thursday. The Islamic State briefly captured the town, previously controlled by the Nusra Front, for several hours.
An activist from the Deir el-Zour who is currently in Turkey told The Associated Press that Nusra Front fighters and their allies brought reinforcements into Bukamal and forced out Islamic State gunmen after midnight Friday following hours of intense fighting that killed more than 50 people.
The man, who spoke on condition of anonymity for fear of reprisals against his relatives in the province, said the Islamic State took its rivals by surprise when its members stormed Bukamal at dawn Thursday and marched through the city.
The Observatory said of the 68 killed in the fighting, some were "executed" by members of the Islamic State.
An amateur video released by the Observatory showed several men, including some who were handcuffed, shot in the head in a square in Bukamal. The narrator said the men were killed by Islamic State members.
The video appeared genuine and corresponded to other Associated Press reporting of the events.
Meanwhile, Syria's state news agency SANA said Friday that authorities liberated an Austrian lawyer identified as Anton Sander, whom it said had be held by rebels in the central city of Homs for the past four months.
SANA said Sander was in Homs visiting friends when he was taken by opposition fighters. It said he recently fled from his captors and was able to flee the neighborhood with the help of authorities.
SANA published several photographs of Sander showing what it described as injuries from torture on his back.
Syria's uprising, which began with largely peace protests in March 2011, has evolved into a civil war with sectarian overtones.
Islamic extremists, including foreign fighters and Syrian rebels who have taken up hard-line al-Qaida-style ideologies, have played an increasingly prominent role among fighters, dampening the West's support for the rebellion to overthrow Assad.
That has led to a backlash by Islamic brigades and more moderate rebels who have launched a war against the Islamic State. Fighting between opposing rebel groups has killed more than 4,000 people since the beginning of the year, activists say.